Tag Archives: notes

To understand these terms clearly, we need to know how JavaScript implemented.

Indeed, a complete JavaScript implementation is made up of three distinct parts

The Core (based on ECMAScript spec)

The Document Object Model (DOM)

The Browser Object Model (BOM)

ECMAScript

ECMA-262 describes it like this“ECMAScript can provide core scripting capabilities for a variety of host environments, and therefore the core scripting language is specified…apart from any particular host environment.”

A Web browser is considered a host environment for ECMAScript, but it is not the only host environment. A list of other host environments listed here.

Apart from DOM and BOM, each browser has its own implementation of the ECMAScript interface.

Document Object Model (DOM)

The Document Object Model (DOM) is an application programming interface (API) for HTML as well as XML.

The DOM maps out an entire page as a document composed of a hierarchy of nodes like a tree structure and using the DOMAPI nodes can be removed, added, and replaced.

DOM level 1 consisted of two modules: the DOM Core, which provided a way to map the structure of an XML-based document to allow for easy access to and manipulation of any part of a document, and the DOM HTML, which extended the DOM Core by adding HTML-specific objects and methods.

DOM Level 2 introduced several new modules of the DOM to deal with new types of interfaces:

DOM Views — describes interfaces to keep track of the various views of a document (that is, the document before CSS styling and the document after CSS styling)

DOM Level 3 further extends the DOM with the introduction of methods to load and save documents in a uniform way (contained in a new module called DOM Load and Save) as well as methods to validate a document (DOM Validation). In Level 3, the DOM Core is extended to support all of XML 1.0, including XML Infoset, XPath, and XML Base.

Note that the DOM is not JavaScript-specific, and indeed has been implemented in numerous other languages. For Web browsers, however, the DOM has been implemented using ECMAScript and now makes up a large part of the JavaScript language.

Other DOMs

Scalable Vector Graphics (SVG)

Mathematical Markup Language (MathML)

Synchronized Multimedia Integration Language (SMIL)

Browser Object Model (BOM)

Browsers feature a Browser Object Model (BOM) that allows access and manipulation of the browser window. Using the BOM, developers can move the window, change text in the status bar, and perform other actions that do not directly relate to the page content.

Because no standards exist for the BOM, each browser has its own implementation.

XML is designed to transport and store data. HTML was designed to display data.

XML documents must have a root element

An XML element is everything from (including) the element’s start tag to (including) the element’s end tag

XML elements must have a closing tag, must be properly nested

Use elements for data. Use attributes for information that is not relevant to the data.

XML tags are case sensitive

XML attribute values must be quoted

Any name can be used, no words are reserved.

<!– This is a comment –>

There are 5 predefined entity references in XML:

&lt;

<

less than

&gt;

>

greater than

&amp;

&

ampersand

&apos;

‘

apostrophe

&quot;

“

quotation mark

White-space is Preserved in XML

With XML, errors are not allowed

Errors in XML documents will stop your XML applications.

XML Elements are Extensible

Raw XML files can be viewed in all major browsers.

It is possible to use CSS to format an XML document. Formatting XML with CSS is not the most common method. W3C recommend using XSLT instead.

XSLT is the recommended style sheet language of XML. XSLT (eXtensible Stylesheet Language Transformations) is far more sophisticated than CSS. XSLT can be used to transform XML into HTML, before it is displayed by a browser